(i) Field of the Invention
The present invention relates to a sheet post-processing device which matches a plurality of piled sheets with images formed thereon conveyed from a copying machine, a facsimile machine, a printer or another image forming device to staple the plurality of sheets.
(ii) Description of the Related Art
Sheets with images formed thereon by the image forming device are continuously piled onto a sheet processing tray (hereinafter referred to as the processing tray) of a sheet processing device (hereinafter referred to as the post-processing device). A bunch of a predetermined number of sheets piled on the processing tray are matched, then stapled, and sent toward a sheet accumulating tray (hereinafter referred to as the accumulating tray) which is adjacent to the post-processing device.
In the post-processing device, in order to staple at least one predetermined portion of the sheet bunch on the processing tray, stapling can be performed while moving a stapling device (hereinafter referred to as the stapler) transversely across the processing tray over a side face of the sheet bunch. However, when the stapler is moved in a position above a surface of the processing tray and along a sheet conveying port from the image forming device, a cost of mechanical components for the purpose is raised, and it is difficult to secure an arrangement space of the mechanical components.
To solve the problem, in a conventional art, a processing device is used in which when a sheet bunch is stapled, predetermined portions of the sheet bunch are stapled by moving the sheet bunch instead of moving the stapler. The sheet bunch stapled on the processing tray is transferred toward the accumulating tray adjacent to the processing device in a direction orthogonal to a direction in which sheets are conveyed from the image forming device. Therefore, if the sheet bunch is stapled while being transferred, the stapler does not need to be moved.
For this reason, in the conventional processing device, the stapler is fixedly disposed in one end of the processing tray to which the sheet bunch is sent, while a sheet holding means (referred to as the holding means) serving as a sheet transfer means for transferring the sheet bunch is disposed in the other end of the processing tray, so that when the sheet bunch is transferred to the stapler by the holding means, the predetermined portion of the sheet bunch is stapled by the stapler.
In this case, the stapler requires to staple a portion closely adjacent to the end of the sheet bunch in a sheet-bunch transfer direction. Therefore, as aforementioned, the stapler needs to be disposed in one end of the processing tray in the sheet-bunch conveying direction and close to the sheet-bunch end in the sheet-bunch transfer direction. Furthermore, the holding means needs to be disposed in the other end of the processing tray and outside the sheet conveying port from the image forming device.
For this end, a transverse width of a processing-device housing is determined by considering at least a width (determined by a maximum width of the sheet to be processed) of the sheet discharge port disposed on the processing tray, a size of the stapler disposed in one end on the processing tray and a size of the holding means disposed in the other end on the processing tray. As a result, the transverse width of the processing device should be large-sized.